[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Author: pre-commit-ci[bot]

data_structures/linked_list/xor_linked_list.py

@@ -55,4 +55,5 @@ def to_list(self) -> list[int]:
 
 if __name__ == "__main__":
     import doctest
+
     doctest.testmod()